Berlin 2014 – scientific programme
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A: Fachverband Atomphysik
A 17: Quantum Protocols and Gates SYQR 3 (with Q)
A 17.4: Talk
Tuesday, March 18, 2014, 11:15–11:30, Kinosaal
A quantum byte with 10−4 crosstalk for fault-tolerant quantum computing — •Christian Piltz, Theeraphot Sriarunothai, Andrés Varón, and Christof Wunderlich — Department Physik, Universität Siegen, 57068 Siegen, Germany
A prerequisite for fault-tolerant and thus scalable operation of a quantum computer is the use of quantum error correction protocols. Such protocols come with a maximum tolerable gate error, and there is consensus that an error of order 10−4 is an important threshold. This threshold was already breached for single-qubit gates with trapped ions using microwave radiation. However, crosstalk - the error that is induced in qubits within a quantum register, when one qubit (or a subset of qubits) is coherently manipulated, still prevents the realization of a scalable quantum computer. The application of a quantum gate - even if the gate error itself is low - induces errors in other qubits within the quantum register.
We present an experimental study using quantum registers consisting of microwave-driven trapped 171Yb+ ions in a static magnetic gradient. We demonstrate a quantum register of three qubits with a next-neigbour crosstalk of 6(1) · 10−5 that for the first time breaches the error correction threshold. Furthermore, we present a quantum register of eight qubits - a quantum byte - with a next-neighbour crosstalk error better than 2.9(4)· 10−4. Importantly, our results are obtained with thermally excited ions far above the motional ground state.